1. Field of the Invention
This invention relates to the preparation of polyurethane-polyurea elastomers. More particularly this invention relates to the utilization of lactones and lactams in the preparation of prepolymers based on diphenylmethane diisocyanate and uretonimine-modified diphenylmethane diisocyanate with either a polyester polyol or a polyoxyalkylene polyether polyol. The prepolymers are employed in the preparation of improved polyurethane-polyurea products.
2. Description of the Prior Art
U.S. Pat. Nos. 4,195,148 and 4,234,445 teach the use of a lactone as a viscosity modifier in the preparation of polyurethanes.
It has been discovered that lactones and lactams act as freezing point depressants for isocyanate terminated prepolymers as well as improving the cold temperature flexibility of polyurethane-polyurea products prepared from these prepolymers. These prepolymers are especially useful in preparing polyurethane microcellular foam systems having enhanced properties for applications such as shoe soles, tires, machine parts, toys, and reaction injection molded products. These prepolymers are also useful in the manufacture of cast elastomer products such as wheels, car mats and the like.